Good ventilation is one of the most practical things a landlord can get right. It reduces condensation, slows mould growth, improves air quality and helps tenants stay healthier through winter. It is also a legal requirement under the Healthy Homes Standards.
This article covers what landlords need to know about ventilation in rental properties, including the common problems, simple solutions and what the Healthy Homes ventilation standard requires.
Quick Answers
What does the Healthy Homes ventilation standard require for rental properties?
According to Tenancy Services, all habitable rooms must have at least one openable window, door or skylight opening to the outside, with a combined openable area of at least 5% of the room’s floor area. Kitchens and bathrooms must also have extractor fans vented to the outside or an approved continuous mechanical ventilation system. Since 1 July 2025, all private rental properties in New Zealand must comply with these requirements.
What is a healthy humidity level in a rental home during winter?
According to Level (a BRANZ-supported building knowledge resource) and NZS 4303:1990 Ventilation for Acceptable Indoor Air Quality, indoor relative humidity should generally remain below 60% to help reduce the risk of mould, dust mites and condensation. A basic hygrometer can help tenants monitor moisture levels inside the home.
How does poor ventilation cause problems in a rental property?
Poor ventilation traps moisture inside the home. This leads to condensation on windows and walls, mould growth on surfaces and soft furnishings, and poor air quality. Older properties without double glazing or centralised ventilation systems are especially prone to these problems.
Can airing out a home actually kill mould?
No. Opening windows and improving airflow helps prevent mould by reducing moisture, but it will not kill existing mould. Mould on hard surfaces needs to be cleaned with an appropriate product. Soft furnishings with mould should be professionally cleaned or replaced.
Why Older Rental Properties Struggle with Ventilation
Older rental properties tend to have worse ventilation than newer builds. This is a problem that Crockers Property Management sees regularly across Auckland’s rental stock.
The two most common issues are single-glazed windows, which cause significant condensation in winter, and the absence of any centralised ventilation system. Many older villas were simply not built with ventilation in mind. They rely on draughts and open windows, which is not practical in winter.
Newer builds and apartments are generally much better. They tend to have double glazing, extractor fans in kitchens and bathrooms, and often positive pressure or heat recovery ventilation systems. As Auckland’s rental market shifts toward more apartments and new builds, the proportion of poorly ventilated older stock is reducing. However, older villas and bungalows remain a significant part of the rental market and require more attention from landlords.
If you own an older rental property, it is worth assessing the ventilation honestly. A property manager can help identify what upgrades may be needed.
For more information refer to our article on Energy Efficient Ways to Keep Your House Warm
What is a Healthy Humidity Level for a Rental Home?
According to Level and NZS 4303:1990 Ventilation for Acceptable Indoor Air Quality, indoor relative humidity should generally remain below 60% to help reduce the risk of mould, dust mites and condensation. In practice, a healthy home will often sit somewhere in the 40% to 60% range, though this varies by season, location and the construction of the home.
Excess moisture creates conditions where mould spores settle more easily on surfaces. Tenants with respiratory conditions are particularly affected by poor indoor air quality caused by high humidity and mould.
Humidity is easy to monitor. Basic hygrometers are inexpensive and widely available. Some smart home devices and apps can track humidity levels and even automate heat pumps to help keep moisture under control.
Landlords cannot control exactly how tenants use a property, but providing the right equipment and clear information gives tenants a better chance of keeping humidity at a reasonable level.
What Simple Steps Help Reduce Moisture and Condensation?
Reducing moisture in a rental property does not require expensive upgrades in most cases. The steps below make a real difference, especially in older properties.
For Tenants
| Action | Benefit |
| Open windows for 10 to 15 minutes each day, even in winter | Flushes humid air out of the home |
| Air out the home during the warmest part of the day | More effective at releasing moisture |
| Open windows or doors at opposite ends of the home at the same time | Creates cross-ventilation and improves airflow |
| Wipe condensation off windows each morning | Removes moisture before it spreads to frames and walls |
| Use extractor fans when cooking or showering | Removes moisture at the source |
For Landlords
- Ensure extractor fans in kitchens and bathrooms are working and venting to the outside.
- Consider installing a heat pump with a dehumidifier function in properties with persistent moisture problems. Note that a heat pump can help reduce moisture and improve comfort, but it does not replace the ventilation requirements under the Healthy Homes Standards.
- Check that any existing ventilation systems are clean and functioning.
- For older properties with single glazing, secondary glazing or thermal curtains can reduce condensation noticeably.
Does Poor Ventilation Damage Rental Property Furnishings?
Yes. Mould grows on soft furnishings, curtains, mattresses and clothing when humidity stays high for extended periods. Excess moisture can also contribute to poorer indoor air quality more broadly. Once mould takes hold, it is difficult and costly to remove.
Hard surfaces such as walls, window frames and bathroom tiles can be cleaned with appropriate products. Bleach and white vinegar are commonly used, though landlords and tenants should check the surface type before applying either. Soft furnishings that have mould growth may need professional cleaning or replacement.
The important distinction for landlords is that improving ventilation and reducing humidity slows mould growth but does not remove existing mould. If a property already has a mould problem, it needs to be dealt with directly before ventilation improvements will make a meaningful difference.
What Does the Healthy Homes Ventilation Standard Require?
According to Tenancy Services, New Zealand’s Healthy Homes Standards set minimum requirements for rental properties across several areas, including heating, insulation, ventilation, moisture management and draught stopping. The ventilation standard is one landlords need to understand clearly.
According to Tenancy Services’ Healthy Homes ventilation standard:
- All habitable rooms must have at least one window, door or skylight that opens to outside and can be fixed in the open position.
- The combined openable area in each room must be at least 5% of that room’s floor area.
- Kitchens and bathrooms must have an extractor fan that vents to the outside, or a continuous mechanical ventilation system that meets the required specifications.
| Requirement | Healthy Homes Ventilation Standard |
| Openable windows | Required in all habitable rooms |
| Minimum openable area | At least 5% of room floor area |
| Kitchen extractor fan | Required, must vent outdoors |
| Bathroom extractor fan | Required, must vent outdoors |
| Alternative to extractor fan | Continuous mechanical ventilation meeting required specifications |
Since 1 July 2025, all private rental properties in New Zealand are required to comply with the Healthy Homes Standards. Landlords who are unsure whether their property meets the ventilation standard should check the current Tenancy Services guidance or seek professional advice.
The Healthy Homes Standards are enforced. Landlords who do not meet the requirements can face financial penalties. If you are unsure whether your property is compliant, getting a proper assessment is the practical step.
For additional information read our article: Healthy Homes Standards in NZ. The Auckland Landlord Guide for 2026
Practical Example:
A Common Ventilation Problem in an Older Auckland Villa
Consider a typical older Auckland villa with single-glazed windows, no extractor fan in the bathroom and no centralised ventilation. In winter, tenants keep windows closed for warmth. Showers, cooking and breathing all add moisture to the air. Condensation forms on windows every morning. Over weeks, mould starts to appear on the bathroom ceiling and on curtains near windows.
This is not an unusual situation. It is one Crockers Property Management encounters regularly in older Auckland rental properties.
The fix usually involves a combination of: installing an extractor fan that vents to the outside (often a Healthy Homes requirement), adding a heat pump with dehumidifier capability, and giving tenants clear guidance on daily ventilation habits.
None of these steps is especially expensive, but the cost of not addressing the problem, including mould remediation, damaged furnishings and potential Healthy Homes penalties, is considerably higher.
What Does This Mean for Landlords?
Since 1 July 2025, full compliance with the Healthy Homes Standards is required across all private rental properties in New Zealand. For ventilation, that means landlords need to check the following:
- Every habitable room has at least one openable window, door or skylight that can be fixed open.
- The combined openable area in each room is at least 5% of that room’s floor area.
- Kitchens and bathrooms have working extractor fans that vent to the outside.
- Any ventilation systems in the property are clean, functional and meet the required specifications.
For older properties, particularly villas and bungalows, this often means some level of upgrade is needed. Extractor fans are the most common gap. Single glazing and a lack of cross-ventilation are also common issues that, while not always a direct compliance failure, contribute significantly to condensation and mould problems.
If you are not sure whether your property meets the current requirements, a property manager or building assessor can help you identify what needs attention before it becomes a compliance issue or a maintenance cost.
Key Takeaways
- Good ventilation in a rental property reduces condensation, slows mould growth and supports tenant health.
- Older properties, especially villas without double glazing or extractor fans, are most at risk of ventilation problems.
- Since 1 July 2025, all private rental properties in New Zealand must comply with the Healthy Homes ventilation standard. This includes openable windows in all habitable rooms and extractor fans in kitchens and bathrooms.
- Opening windows for 10 to 15 minutes daily, using extractor fans and wiping condensation each morning are practical steps that make a real difference.
- Improving ventilation prevents mould but will not remove existing mould. Active mould needs to be cleaned or professionally treated.
Final Thoughts
Ventilation is one of those property issues that is easy to overlook until it becomes a problem. For landlords, the combination of Healthy Homes compliance obligations and the practical costs of mould, condensation and unhappy tenants makes it worth getting right.
Older Auckland properties in particular need attention. They were not built with modern ventilation standards in mind, and without some level of upgrade or at least good tenant guidance, moisture problems are almost inevitable in winter.
The good news is that the basics are not complicated. Openable windows, working extractor fans, a heat pump and a conversation with tenants about daily ventilation habits will cover most situations.
Need Help With Your Rental Property?
If you are unsure whether your rental property meets the current Healthy Homes ventilation requirements, or you want practical advice on managing an older property, the Crockers Property Management team can help. Get in touch for a straightforward conversation about what your property may need.
A FREE Crockers rental appraisal will give you a clear picture of your property's market position, and our team can point you toward the right next steps for compliance, including who to engage for an assessment.
Article written by Shanon Aitken, Crockers Property Management
This article was prepared by the Crockers Property Management team, drawing on their experience managing rental properties across Auckland. It is intended as general guidance only and does not constitute legal advice. Landlords should verify current legislative requirements with Tenancy Services or a qualified professional.
